1. Field of the Invention
The invention relates to a method of transmitting n-bit information words, comprising an encoding step in which n-bit information words are converted into m-bit code words, m being greater than n, a transmission step for transmitting the m-bit code words, and a decoding step in which the transmitted m-bit code words are reconverted into n-bit information words.
The invention also relates to an information-transmission system for carrying out such a method, comprising an encoding device which is adapted to receive n-bit information words and to convert the received n-bit information words and into m-bit code words, a decoding device which is adapted to receive the m-bit code words and to reconvert the received code words into n-bit information words.
The invention further relates to an encoding and decoding device for use in the transmission system.
2. DESCRIPTION OF THE RELATED ART
A method, a transmission system, an encoding device and a decoding device as described in the opening paragraphs are known inter alia from European Patent Application EP No. 0,150,082 (PHN 11.117).
The above-mentioned method is often used to improve the quality of the information transmission. The use of code words having a larger number of bits than the information words ensures that the number of code words which may be used is larger than the number of different information words. For this purpose those code words are then selected which in conformity with a predetermined criterion are most suited for information transmission.
In the above-mentioned Application it is stated that n-bit information words can be converted into m-bit code words by means of a look-up table which stores an m-bit code word for every n-bit information word. In a similar way m-bit code words are converted into n-bit information words after transmission. A drawback of this is that the number of components required for the encoding device and decoding device is large. For example, when a memory is used to store the look-up table the number of storage locations required for this is equal to 2.sup.n .times.m. When the codes are converted by means of gate circuits the number of gates required is also substantial.